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OS X and iOS Kernel Programming by Douglas Clarke, Ole Henry Halvorsen

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Memory Descriptors

Memory descriptors are implemented by the IOMemoryDescriptor class and is fundamental to working with memory in I/O Kit. The class also serves as a super class for other important memory-related classes, which we will discuss later in this chapter. Many parts of the I/O Kit accept an IOMemoryDescriptor as an argument. For example, the USB family uses the class to describe memory used for USB read and write requests.

The IOMemoryDescriptor describes the properties of a memory buffer or range of memory, but does not allocate (or free) the described memory. It contains metadata and allows some operations to be performed on the memory. It can describe virtual and physical memory. The class is versatile and can be used for a number ...

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